Tape ball grid array (BGA) or quad-flat no lead (QFN) packages with wirebonds are the dominant solution for producing low-cost electronic packages. FIG. 1 provides an illustration of an exemplary tape BGA package 100 that utilizes wirebonds. As illustrated, the package substrate 110 is a thin tape substrate. Conductive traces 124 may be formed over a surface of the tape substrate. For example, the conductive traces may be copper traces. The conductive traces 124 may be covered by a layer of solder resist 112. Solder resist openings 128 may be formed over portions of the conductive traces 124 to provide an opening where the wires 144 may be bonded. Wires 144 may connect the conductive traces 124 to wirebond pads 146 formed on a top surface of the device die 130. The wires 144 electrically couple the integrated circuitry (not shown) in the die 120 to the solder bumps 138 on the backside of the package substrate 110. The conductive traces 124 may be electrically coupled to the solder bumps 138 by conductive through vias 126. The device die 130 may be attached to the solder resist layer 112 by a die attach paste 149. The entire package may be covered by an encapsulation layer 140, such as an epoxy encapsulation.
However, the use of wirebond packages has significant drawbacks. For example, connecting wires to a top surface of the device die 130 results in a package thickness that is greater than electronic packages that utilize alternative interconnect techniques such as flip-chip or controlled collapsed chip connection (C4) techniques. Additionally, device dies that are packaged with wirebonding require additional processing operations to form the wirebond pads 146.
Despite the limitations associated with wirebonding, device packages formed on thin and flexible substrates have not been able to utilize flip-chip bonding for multiple reasons. First, special substrate handling systems would be required to process the tape substrate because the tape substrate is thin and flexible. The additional equipment and processing operations needed to accommodate the substrate results in an increase in the overall cost of the package. Additionally, flip-chip bonding may include a mass reflow operation. The increase in temperature during the mass reflow causes the tape substrate to permanently deform. Additionally, it may not be economically feasible to substitute thermal compression bonding (TCB) for the mass reflow process due to the high cost of TCB. Therefore, flip chip bonding that utilizes TCB instead of a mass reflow may not be an economically viable process for producing low-cost electronic packages on tape substrates.